KR900010850Y1 - Focus compensating circuit for crt. - Google Patents

Abstract

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Description

CRT focus correction circuit

1 is a circuit diagram of the present invention.

2 is a waveform diagram of each part of FIG.

* Explanation of symbols for main parts of the drawings

1: Input terminal 10: Correction unit

20: amplification unit C ₁ -C ₈ : condenser

R ₁ -R ₄ : Resistance VR ₁ : Variable resistor

VL ₁ : Variable coil DY: Deflection coil

Q ₁ : Transistor B ⁺ : Power

The present invention relates to a focusing circuit of a cathode ray tube in which the amount of electron beams scanned on the fluorescent surface of the cathode ray tube is made constant.

In general, the amount of electron beams scanned on the fluorescent surface becomes high at the center of the fluorescent screen and becomes smaller at both sides. Conventionally, the focus of the CRT is adjusted by giving a voltage difference to the grid of the CRT and making the left and right voltages of the CFL higher than the voltage difference at the center. However, the focusing error caused by the characteristics of the deflection coil of the CRT could not be compensated.

An object of the present invention is to provide a focus correction circuit for a cathode ray tube to correct an error caused by the characteristics of the cathode ray tube and the deflection coil by using a variable resistor and a variable coil. It is configured to be adjusted through a connected variable resistor and a variable coil.

This will be described in detail with reference to the accompanying drawings.

After the voltage waveform of the video signal of the input terminal 1 applied to the deflection coil DY and the linearity correcting capacitor C ₁ is applied to the variable resistor VR ₁ through the DC blocking capacitor C ₂ . The compensator 10 is configured to be applied to the base side of the amplifying transistor Q ₁ through the variable coil VL ₁ , the resonant capacitor C ₃ , C ₄ , and the DC blocking capacitor C ₅ . The power supply B ⁺ forms the transistor Q ₁ through the noise canceling capacitor C ₆ and the bias resistors R ₁ -R ₄ to amplify the amplification unit 20 so as to amplify the output of the correction unit 10. It is configured to drive the output of the amplifier 20 is applied to the second grid of the CRT through the DC blocking capacitor (C ₈ ).

Reference numeral C ₇ is a high-pass compensation capacitor connected to the emitter side of the transistor Q ₁ .

FIG. 2A is a waveform diagram of each part of FIG. 1, and FIG. 2E is a character time waveform diagram of a fluorescent surface.

Referring to the effects of the present invention configured as described above are as follows.

The voltage waveform of the video signal of the input terminal 1 as shown in FIG. 2 (a) passing through the deflection coil DY and the linearity correcting capacitor C ₁ is transmitted through the DC blocking capacitor C ₂ . VR ₁ ) is applied to the waveform as shown in FIG. 2B and is converted into the waveform as shown in FIG. 2C after being resonated through the variable coil VL ₁ and the resonant capacitor C ₃ and C ₄ . It is applied to the base side of the transistor Q ₁ through the blocking capacitor C ₅ .

Then, the power supply B ⁺ of 400-700V "turns on" transistor Q ₁ through the bias resistors R ₁ -R ₄ so that the power supply B ⁺ is applied to the base side of transistor Q _{1 in} FIG. As the waveform is inverted and amplified, the waveform as shown in FIG. 2 (d) is generated on the collector side of the transistor Q ₁ , and is then applied to the second grid of the CRT through the DC blocking capacitor C ₈ to always be in a constant state. By compensating the focused voltage time waveform diagram of FIG. 2e, the focus of both the center and the central portion of the fluorescent surface can be made constant.

Wherein the transistor (Q _1), as when the error occurs in the focus of the center of the fluorescent screen and on both sides by the characteristics of the cathode ray tube by varying the variable resistance (VR ₁₎ FIG. 2 (b) to adjust the waveforms to the 0-6V The focus of the CRT can be made constant by changing the voltage waveform of FIG.

Then, when the focus of the center and both portions does not coincide due to the characteristic difference between the deflection coil (DY) and the CRT, the variable coil (VL ₁ ) is varied so that the variable coil (VL ₁ ) and the condenser (C ₃ ) (C ₄ ) The time constant of the waveform of FIG. 2 (d) applied to the second grid of the CRT through transistor Q ₁ changes as the time constant of is changed to the broken line portion of FIG. By correcting the focal time waveform diagram of FIG. 2E, the focus of the fluorescent surface can be made constant.

Therefore, the focus error of the fluorescent surface caused by the characteristics of the deflection coil (DY) and the cathode ray tube is adjusted through the correction unit 10 to adjust the second grid of the cathode ray tube. It can be used for monitor circuit for program control and monitor circuit for program control.

As described above, the present invention is configured to adjust the focus of the fluorescent screen through the variable resistor and the variable coil connected between the deflection coil and the CRT. The defects of the CRT and the deflection coil can be eliminated and the focus of the fluorescent screen is improved. This is an effect that can be improved.

Claims (1)

In a circuit in which the video signal of the input terminal 1 applied to the deflection coil DY is applied to the second grid of the CRT through the amplification unit 20 composed of the transistor Q ₁ , the deflection coil DY and the amplification. The video signal applied to the deflection coil DY is connected between the units 20 so that the video signal is supplied through the variable resistor VR ₁ and the variable coil VL ₁ , and the time constant is changed through the capacitor C ₃ (C ₁ ). And a correction tube (10) configured to adjust the amplifying transistor (Q ₁ ) through the condenser (C ₅ ).